Coplanar X-Ray Guided Aiming Arm for Locking of Intramedullary Nails

ABSTRACT

A novel coplanar X-ray guided method and aiming arm device for insertion of distal locking screws in intramedullary bone nails. Radiopaque target markers in the aiming arm enable the easy positioning of an X-ray source such that an X-ray beam is coplanar with the aiming arm transverse holes. After the X-ray source is accurately oriented, a single X-ray snapshot is enough to assess the exact distortion of the implanted intramedullary nail. The X-ray beam need not be coaxial with the nail holes. The aiming arm includes a mobile portion and a fixed portion fastened to the nail, and the aiming arm can be adjusted, displacing the mobile portion over the fixed portion, to compensate for the distortion of the intramedullary nail caused by implantation in bone.

PRIORITY CLAIM

The present application (a) is a Continuation Application of U.S. patentapplication Ser. No. 10/947,155 filed on Sep. 23, 2004 entitled“Coplanar X-Ray Guided Aiming Arm for Locking of Intramedullary Nails”and (b) has a copending related U.S. patent application Ser. No.11/240,785 filed on Sep. 23, 2005 entitled “Coplanar X-Ray Guided AimingArm for Locking of Intramedullary Nails.” The disclosure of theseapplications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention is directed to aiming arm locking ofintramedullary nails, and in particular to X-ray guided aiming armlocking of intramedullary nails.

It is well known the use of intramedullary nails to treat bone fracturesin tubular bones. A nail is implanted in the medullary canal of the boneacross the fracture site in order to retain the bone fragments on thebone nail and to secure the bone fragments from being displaced. Thenail has transverse holes and is fixed to the bone by a number oflocking screws or fixation bolts which must pass through holes in thenail and into the surrounding bone material. After the nail is insertedinto the medullary canal, the distal end of the nail is invisible to thenaked eye. Numerous methods and apparatus have been developed tosuccessfully place locking screws across both a fractured bone and animplanted intramedullary nail.

Usually nails are locked at both ends, close to the entry point and faraway from the entry point. The region of the bone where the nail isimplanted is identified as proximal and the opposite end of theintramedullary nail is distal. Nail locking is currently made usingeither mechanical aiming arms or X-ray guidance.

Mechanical aiming instruments, which are fixedly attached to theproximal end of the implanted bone nail, may provide concentricalignment with the proximal screw holes in order to enable reliabledrilling such as those disclosed in U.S. Pat. Nos. 5,334,192, 5,766,179,and 6,514,253.

An advantage of this mechanical aiming arm is that neither the patientnor the surgeon will be exposed to X-ray source. However, distal screwholes may not perform satisfactorily due to distortion of theintramedullary nail while being driven into the bone and/or mechanicalstress on the aiming arm. Aiming-arm-guided-locking is usuallysuccessful for proximal locking since the distortion of the nail whileinserted into the bone is negligible for a short length of nail.However, it is usually not successful for distal locking except for veryshort nails since the distortion of the nail while inserted into thebone is not negligible.

Distortion in the implanted intramedullary nail happens in the 3D spaceand can be analyzed into its main components:

Length variation in the axis of the intramedullary nail.

Rotational distortion in the axis of the intramedullary nail.

Flexion distortion in the plane of the intramedullary nail distal holes

Flexion distortion perpendicular to the plane of the distal holes of theintramedullary nail.

We can accept, when using non slotted intramedullary nails provided ofcoplanar distal holes, that the first three mentioned distortions:length distortion in the axis of the nail, rotational distortion in theaxis of the nail, and flexion deformity in the plane of the distal screwholes of the nail, are negligible for our task of distal locking.However, flexion distortion in a plane perpendicular to the plane of thedistal screw holes of the nail is very important and the one thatconcerns when distal locking is the subject of matter.

X-ray guidance is what is presently most used for distal locking exceptfor very short nails. The procedure starts by exactly positioning theX-ray beam in the axis of the nail holes, something that is not alwaysstraightforward for the X-ray technician. The intramedullary nail willcast a dark, elongate image on the X-ray monitor, while the nail holeswill appear as light circles or ovals. In particular, the nail hole willappear as a circle when the X-ray source is positioned such that theX-ray beam is parallel to the axis of the nail hole, something that is acomplex 3D procedure.

After the nail holes have been located, a drill is used to drill throughthe bone for insertion of the locking screw. This procedure may beaccomplished either with or without the use of an aiming arm guide,wherein said aiming arm guide can be fastened to the bone nail or not.

Various aiming guides are already known in the art to be used inconjunction with the X-ray source in order to accurately place thelocking bone screws across both a fractured bone and an implantedintramedullary nail, such as those disclosed in U.S. Pat. Nos.4,803,976, 4,850,344, 6,656,189, 4,667,664, and 4,881,535.

All these X-ray guided procedures require the X-ray source positionedsuch that the X-ray beam is parallel to the axis of the nail hole. Thisis not always simple, and sometimes not even possible. It may alsoincrease undesirable X-ray exposure to the surgeon, patient andoperating room staff, and lengthen the surgical procedure.

Attempts have been made in the past to obtain a successful method fordistal locking, which overcome the problems associated with X-ray guidedlocking. However, most of these systems are cumbersome and requireadditional bone screw holes in order to exactly assess the position ofthe hole in the distorted intramedullary nail after implanted into thebone.

The present invention relates to a novel apparatus and method of distallocking that allows the surgeon to target and install bone screws intoan intramedullary nail in an accurate, fast and reliable manner.

BRIEF SUMMARY OF THE INVENTION

Is therefore an object of the present invention to provide an aiming armcapable of being adjusted to compensate for the intramedullary naildistortion after its insertion into the bone, making use of theinformation given by a few snap shots of the X-ray image intensifier.

Another object of the present invention is to provide a radiolucentaiming arm for distal locking of an intramedullary nail provided ofradiopaque target markers capable to determine when the position of an Xray source is such that an X ray beam is coplanar with the aiming armholes axis.

Further, it is an object of the present invention to reduce undesirableX-ray exposure to the surgeon, patient and operating room staff.

The present invention by being an easy and straightforward procedure forthe X-ray technician and the surgeon makes distal bone fixation ofintramedullary nails simple and fast overcoming one of the mostimportant subject of matter of actual surgery, time shortening.

The aiming arm of the present invention overcomes the disadvantages ofconventional aiming arms by providing an easy obtainable X-ray guidancefor distal locking without the requirement of the X-ray beam to becoaxial with the nail hole, so that reducing undesirable X-ray exposureto the surgeon, patient and operating room staff.

The novel feature of the present invention is an aiming arm capable ofbeing adjusted to compensate for the nail deformation after itsinsertion into bone, making use of the information given by a few snapshots of the X-ray image intensifier.

By fulfilling the recently mentioned objects, the present invention isextremely helpful to the medical care area.

The preferred embodiment of the present invention provides an adjustableaiming arm fastened to a bone nail. The aiming arm is constructed of aradiolucent material and has coplanar transverse holes or apertures. Theaiming arm has a number of radiopaque target markers to enable the X-raytechnician to assess when the position of an X-ray source is such thatan X-ray beam is coplanar with the transverse holes of aiming arm. Theimage shown by a single X-ray snapshot in this position gives thesurgeon precise information on the amount of nail distortion after nailinsertion into the bone, so that allowing the surgeon to determine theaiming arm adjustment needed to compensate for the distortion of theintramedullary nail. Once the aiming arm is accurately oriented over thenail hole, so as the aiming arm transverse holes are coaxial with thenail holes, the surrounding bone material can be drilled. After the boneis drilled, locking bone screws are screwed through the protectivesleeves previously inserted into the aiming arm transverse holes.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Preferred features of the present invention are disclosed in theaccompanying drawings, wherein similar reference characters denotesimilar elements throughout the several views, and wherein:

FIG. 1 shows a plan view of the aiming arm according to the presentinvention wherein the protective sleeves and a fastened intramedullarynail are shown.

FIG. 2 is a side view illustrating the aiming arm transverse holesprecisely aligned with the intramedullary nail holes.

FIG. 3 shows a perspective view of the aligned aiming arm according tothe present invention, wherein the protective sleeves and theintramedullary nail fastened to the aiming arm are shown.

FIG. 4 shows a side view of the aiming arm according to the presentinvention, wherein the fastened intramedullary nail is distorted afterbone insertion, and wherein aiming arm holes and intramedullary nailtransverse holes are not aligned thereof.

FIG. 5 shows a side view of the aiming arm according to the presentinvention after compensation for the nail deformation was made, so thataiming arm holes and intramedullary nail transverse holes are aligned.

FIG. 6 is a perspective view in the plane of the aiming arm holes,illustrating how the alignment of intramedullary nail cross holes andaiming arm holes can be confirmed despite the fact that the X-ray beamis not aligned with the axis of the intramedullary nail holes.

FIG. 7 shows a perspective view of FIG. 5.

FIG. 8 shows a perspective view of the aiming arm according to thepresent invention wherein a fastened short intramedullary nail implantedinto the bone is shown.

FIG. 9 is a side view illustrating the aiming arm holes preciselyaligned with the short intramedullary nail.

FIG. 10 shows a perspective view of FIG. 9, wherein the protectivesleeves, the short intramedullary nail fastened to the aiming arm andthe front and rear radiopaque markers are shown.

FIG. 11 shows a side view of the aiming arm according to the presentinvention, wherein the fastened intramedullary nail is distorted afterbone insertion, and wherein aiming arm holes and intramedullary nailtransverse holes are not aligned thereof.

FIG. 12 is a perspective view in the plane of the aiming arm holes,illustrating how a single X-ray snapshot in this plane enables to assessthe exact distortion of the intramedullary nail after inserted into thebone.

FIG. 13 shows a perspective view of the aiming arm according to thepresent invention wherein the distorted intramedullary nail, and aninsert with offset holes to compensate for the distortion of theintramedullary nail are shown.

FIG. 14 shows a side view of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a method of bone fixation according to the preferredembodiment of the present invention will be explained with reference toFIGS. 1-7.

Referring to FIG. 1 there is shown an aiming device 4, on which ismounted a mobile aiming arm portion 6. An intramedullary nail 2, withtwo coplanar transverse holes 3 is fastened to the aiming arm 4.Protective sleeves 7 slide through holes 5 located in the mobile part ofthe aiming arm 6, guiding drills and bone screws through the nailtransverse holes 3 for distal locking of the intramedullary nail 2.Mobile part rotates about the axis 9 over aiming arm.

The aiming arm 4 is fastened to the intramedullary nail 2, and beforethe nail 2 is inserted into the bone 1, aiming arm holes 5 andintramedullary nail holes 3 are precisely aligned as shown in FIGS. 2and 3. Plane P defined by the longitudinal axis A of intramedullary nail2 and the axis of the aiming arm transverse holes 5 is shown in FIG. 3.

After implanted, the distortion of the intramedullary nail causes aimingarm holes 5 and intramedullary nail holes 3 non-alignment as shown inFIG. 4.

The aiming arm 4 is mostly made of a relatively radiolucent material andis provided with radiopaque target markers 10, 11, which enable asurgeon to assess when the position of the X ray source is such that anX-ray beam is coplanar with the plane of the aiming arm holes, not beingnecessary for the X ray beam to be coaxial with the intramedullary nailholes 3. As a consequence, a single snapshot of an X ray sourcepositioned such that an X ray beam is coplanar with the aiming arm holes5 is enough to determine the exact distortion of the intramedullary nail2, as shown in FIG. 6.

By turning the adjusting knob 8 the required amount, the mobile part ofthe aiming arm 6 can be positioned to compensate for the distortion ofthe intramedullary nail 2, so that aiming arm holes 5 and nail holes 3are re-aligned as shown in FIGS. 5 and 7.

Once aiming arm holes 5 and intramedullary nail holes 3 are aligned itis easy to slide in the protective sleeves 7 through the aiming armholes 5. After the protective sleeves 7 are positioned, a drill bit isaligned with the nail hole 3 and drilled through the nail hole 3 and thesurrounding bone material. Once the second drill bit is drilledaccurately through the second nail hole 3 and the surrounding bonematerial, the second drill bit is removed, and a locking screw isinserted through the protection sleeve and screwed through the bone andsecond nail hole 3 to secure the nail to the bone. Finally, the firstdrill bit is removed, and a second locking screw is inserted through thesleeve 7 and screwed through the bone 1 and first nail hole 3 to securethe intramedullary nail 2 to the bone 1.

Next, an aiming arm device according to the second embodiment of thepresent invention will be explained with reference to FIGS. 8-14.

Referring to FIG. 8 there is shown an aiming device 14, fastened to ashort intramedullary nail 12. The intramedullary nail 12 is providedwith two coplanar transverse holes 13. Protective sleeves 17 can slidethrough holes 15, existing in the insert 16 situated in the aiming arm14 in order to guide drills and bone screws through the nail cross holes13, for distal locking of the intramedullary nail 12. Insert holes 15,and nail holes 13 have the same axis 19.

The aiming arm 14 provided of radiopaque target markers, bubbles 20 andlines 21, is fastened to the bone nail 12. Before the intramedullarynail 12 is inserted into bone 1, aiming arm holes 15 and nail holes 13are perfectly aligned as it can be seen in FIGS. 9 and 10.

After bone insertion the intramedullary nail 12 commonly distorts suchthat aiming arm holes 15 and nail holes 13 are not aligned anymore asshown in FIG. 11.

A single snapshot of an X ray source positioned such that an X ray beamis coplanar with the aiming arm holes 15 is enough to determine theamount of nail distortion, as shown in FIG. 12.

By using an insert 16, provided with offset holes, aiming arm holes 15and intramedullary nail holes 13 can be aligned again as shown in FIGS.13 and 14.

Once aiming arm holes 15 and intramedullary nail holes 13 are aligned itis easy to slide in the protective sleeves 17 through the aiming armholes 15, to slide in through the protective sleeves 17 the drill tobore the bone 1, and to slide in through the protective sleeve 17 thebone screw which will match the nail hole 13 as it is required to lockthe intramedullary nail 12.

While I have illustrated and described two preferred embodiments of theinvention, it will be understood that those skilled in the art willthereby be enabled to devise variations and modifications withoutdeparting from the spirit and scope of this invention, as defined in theappended claims.

1-15. (canceled)
 16. A bone plate, comprising: a head portion having acurved surface configured and dimensioned to conform to a metaphysis ofa bone; a shaft portion configured and dimensioned to conform to adiaphysis of a bone, the shaft including an anterior fork extendingsubstantially parallel to an anterior of the shaft portion and aposterior fork extending from a posterior of the shaft portion; a firstscrew hole passing through the plate from an outer surface to abone-facing surface of the head portion, the first screw hole beingdimensioned to slidingly receive therein a threaded, bone-engaging shaftof a first screw and including a thread dimensioned to engage acorresponding thread of a head of the first screw to retain the firstscrew seated in the first screw hole for substantially as long as thebone plate is implanted; and a second, non-threaded screw hole passingthrough the plate from an outer surface to a bone-facing surface of theshaft for receiving therein a second screw having a threaded,bone-engaging shaft and a head.
 17. The bone plate of claim 16, whereinthe head portion is twisted.
 18. The bone plate of claim 16, wherein thehead portion is tapered.
 19. The bone plate of claim 16, wherein thehead portion includes at least one suture hole.
 20. The bone plate ofclaim 16, wherein the head portion includes no non-threaded holes. 21.The bone plating system of claim 16, wherein the shaft portionterminates in a tapered tail.
 22. A bone plate defining an outer surfaceand a bone-facing surface, comprising: a curved head portion configuredand dimensioned to conform to a metaphysis of a bone, the head portionincluding first and second threaded holes extending therethrough fromthe outer surface to the bone-facing surface thereof, diameters of thefirst and second holes being different from one another, the threadingof the first and second threaded holes being dimensioned to engagethreadings on heads of first and second screws, respectively; a shaftportion extending from the head portion and configured and dimensionedto conform to a diaphysis of a bone, the shaft portion including ananterior fork extending substantially parallel to an anterior side ofthe shaft portion and a posterior fork extending from a posterior sideof the shaft portion, wherein at least a first threaded hole and asecond threaded hole are located in the head portion, and the firstthreaded hole and the second threaded hole have different diameters; andat least one non-threaded hole passing through the plate from the outerto the bone-facing surface thereof.
 23. The bone plate of claim 22,wherein axes of the first and second threaded holes converge.
 24. Thebone plate of claim 22, wherein axes of the first and second threadedholes converge on a bone-facing side of the plate.
 25. A bone platedefining an outer surface and a bone-facing surface opposite the outersurface, comprising: a head portion configured and dimensioned toconform to a metaphysis of a bone, the head portion including aplurality of first screw holes extending therethrough from the outersurface to the bone-facing surface, each of the first screw holesincluding an internal threading dimensioned to engage a threading formedon a head of a screw to be inserted thereinto; and a shaft portionconfigured and dimensioned to conform to a diaphysis of a bone, theshaft portion including a plurality of second screw holes extendingtherethrough from the outer surface to the bone-facing surface, thesecond screw holes including at least one threaded hole including aninternal threading dimensioned to engage a threading formed on a head ofa screw to be inserted thereinto and at least one non-threaded hole. 26.The bone plate of claim 25, wherein the at least one threaded secondhole has a double lead thread.
 27. The bone plate of claim 25, whereinthe head portion is twisted.
 28. The bone plate of claim 25, wherein thehead portion is tapered.
 29. The bone plate of claim 25, wherein thehead portion is curved.
 30. The bone plate of claim 25, wherein the headportion includes at least one suture hole.
 31. The bone plate of claim25, wherein an end of the shaft portion opposite the head portionterminates in a tapered tail.
 32. The bone plate of claim 25, whereinthe shaft portion has a substantially trapezoidal shaped cross-sectionin a region between the threaded and non-threaded screw holes tominimize contact between the bone-facing surface and a bone on which theplate is mounted.
 33. The bone plate of claim 25, wherein the headportion flares outward from the shaft portion.